People in the study with insomnia symptoms had more heart attacks than people without insomnia symptoms, and those with the most symptoms had the highest risk.

Study researcher Lars Erik Laugsand, MD, of the Norwegian University of Science and Technology, says more research is needed to confirm the findings in different populations and to understand how lack of sleep may affect the heart.

"If the association is confirmed, addressing sleep problems could prove to be an important intervention to lower heart attack risk," he tells WebMD. "Insomnia is quite common and it is fairly easy to treat. People need to be aware of this potential connection."

Insomnia and the Heart

In a recent poll conducted by the National Sleep Foundation, about two-thirds of respondents (63%) reported not getting enough sleep; 43% said they rarely or never got a good night's sleep on weeknights.

Insomnia can include having difficulty falling asleep or staying asleep or having troubled sleep that is not restful and restorative.

Several earlier studies have suggested a link between insomnia and blood pressure. But only a few small studies have examined the effect of poor sleep on heart disease, Laugsand says.

The newly published study included more than 50,000 Norwegian adults enrolled in a national health survey between 1995 and 1997.

During a follow-up of 11 years, 2,386 of the enrollees had first-time heart attacks.

After taking into account known heart attack risk factors like age, blood pressure, cholesterol, and obesity, the researchers found that people with insomnia had more heart attacks than people who rarely had trouble sleeping.

When they considered the most common insomnia symptoms, they found that:

People who had trouble falling asleep most nights over the previous month had a 45% higher risk for heart attacks.

People who had trouble staying asleep had a 30% increase in heart attack risk.

Waking up feeling unrefreshed in the morning more than once a week was associated with a 27% higher heart attack risk.

Preventing Heart Problems

"Evaluation of insomnia might provide additional information in clinical risk assessment that could be useful in cardiovascular prevention," the researchers conclude.

They add that the findings may be unique to high-latitude regions like Norway, where the sun rarely sets in the spring and summer and does not rise in the winter.

The incidence of sleep apnea among the study population was also not known.

Sleep apnea is commonly associated with obesity, which is a risk factor for heart disease and heart attacks.

Cardiologist Edward A. Fisher, MD, PhD, says more study is needed to understand how poor sleep quality affects the heart. Fisher is a professor of cardiovascular medicine at NYU Langone Medical Center in New York.

"If insomnia really is associated with heart attack risk, understanding the underlying mechanism behind this could be very important," he tells WebMD. "But it may not be easy."